The present invention relates to a compressor that is ideal for a vehicle air-conditioning system, and more specifically to a lubrication technique that guides lubricating oil to lubrication target areas, such as the bearing of a drive shaft and the sliding surface between a piston and a cylinder bore.
A compressor that guides lubricating oil to the bearing of a drive shaft is disclosed, for example, in Japanese Laid-Open Patent Publication No. 7-27047. The compressor described in this publication is a swash plate compressor, in which a refrigerant gas that is discharged into a discharge chamber is guided to an oil separator provided in a cylinder block, thereby separating the lubricating oil from the refrigerant gas, and then the separated lubricating oil is guided to the bearing of a drive shaft via an oil supply hole provided in the cylinder block for lubrication.
The compressor configured as described above guides the oil separated from the discharged refrigerant to the bearing for lubrication, using the pressure difference between the oil separation chamber, which is at a higher pressure, and a drive chamber, which is at a lower pressure, and then returns the oil to the drive chamber. Consequently, if the diameter of the lubricating oil supply hole formed in the cylinder block is too large, leakage of the discharged refrigerant causes a degradation in performance, and leakage of a large amount of high-temperature lubricating oil heats the refrigerant that has been drawn in, thereby causing performance degradation. On the other hand, if the oil supply hole is too small, foreign substances, such as sludge (oil sludge), tend to clog the oil supply hole, and manufacturing such a small hole is also difficult.
Especially when a compressor uses carbon dioxide (CO2) as the refrigerant, the operation pressure difference (the difference between a discharge pressure and a suction pressure) is large (5 MPa or greater) and therefore, said conflicting requirements become more difficult to satisfy.
The present invention has been developed in view of said existing problems, and its objectives are to prevent the clogging of the oil supply hole by foreign substances, such as sludge, and to avoid performance degradation caused by leakage of the discharged refrigerant.
In order to achieve the above objectives using a compressor related to the present invention, when a lubricating oil is sent to a lubrication target area via an oil supply hole, a flow rate restriction channel communicated to the outlet of the oil supply hole restricts the flow of the lubricating oil, thereby reducing the flow rate. The channel is defined between a cylindrical hole and a member that rotates or reciprocates inside this cylindrical hole. Consequently, even when foreign substances, such as sludge, flow from the oil supply hole to the channel, the foreign substances are swept out from the outlet of the oil supply hole due to the relative movements of the members that define the channel.
Therefore, according to the present invention, clogging of the oil supply hole by foreign substances can be prevented and performance degradation caused by leakage of the discharged refrigerant can also be avoided.
Moreover, because the channel is defined by a gap between the cylindrical hole and the member that rotates or reciprocates inside the cylindrical hole, the channel can be formed more easily than a case in which a channel is formed by boring.
Note that in this case, the lubricating oil to be sent to the lubrication target area should preferably be lubricating oil that has been separated from the discharged refrigerant, and should preferably be guided based on the pressure difference between the discharged side and the suction side. Such a configuration is especially effective when applied to a compressor that uses carbon dioxide as the refrigerant.
Moreover, when a channel is defined by the gap between the external surface of a rotating member that rotates together with the drive shaft and the internal surface of a circular hole in which the rotating member fits, foreign substances, such as sludge, that flow in via the oil supply hole are swept out from the outlet due to the rotation of the rotating member, thereby preventing the clogging of the oil supply hole, and leakage of the discharged refrigerant is suppressed, thereby avoiding performance degradation.
Note that in this case, it is preferable to provide a foreign substance sweep-out groove on the external surface of the rotating member and the foreign substance sweep-out groove intermittently communicates with the outlet of the oil supply hole. In such a case, whenever the groove faces the outlet of the oil supply hole, foreign substances, such as sludge, that flow in via the oil supply hole can be captured. Therefore, the sweeping of foreign substances, such as sludge, can be more actively performed, making it possible to more effectively prevent the clogging of the oil supply hole.
When the sliding surface between a piston and a cylinder bore is the lubrication target area, the flow rate of the lubricating oil flowing into the sliding surface via the oil supply hole is controlled by the channel defined between the piston and the cylinder bore. When the piston reciprocates inside the cylinder bore, foreign substances, such as sludge, are moved by adhering to the piston or with the lubricating oil. This action prevents the clogging of the oil supply hole and suppresses leakage of the discharged refrigerant, thereby avoiding performance degradation.
Note that in this case, a stepped surface is provided at the boundary between the gap comprising the channel and the side clearance between the external surface of the piston and the internal surface of the cylinder bore. This stepped surface should preferably be provided in a position that crosses the outlet of the oil supply hole when the piston moves toward the bottom dead center. With such a configuration, foreign substances, such as sludge, flowing in via the oil supply hole can be swept out from the outlet of the oil supply hole by the stepped surface. Moreover, it is preferable to use a configuration in which the stepped surface extends outside the cylinder bore when the piston is positioned at the bottom dead center. With such a configuration, the captured foreign substances can be reliably swept out of the cylinder bore through the outlet of the oil supply hole.
Furthermore, the channel defined between the piston and the cylinder bore should preferably comprise a groove that is provided on the external surface of the piston and that extends in the axial direction. With such a configuration, the channel can increase the flow-restriction effect, thereby better restricting leakage of the discharged refrigerant. Moreover, the foreign substances swept out from the oil supply hole should preferably be discharged into a drive chamber having a relatively large space.